New rules lower the size of loans that qualify for the mortgage-interest deduction and curb the amount of property taxes homeowners can deduct

The jumbo-mortgage market has been a bright spot for the banking industry in recent years. The tax law could take some of the shine off it.

The tax-code overhaul, among its many other consequences, eliminates some of the benefits of homeownership, particularly for high-end homes. And the borrowers who buy those homes are exactly whom banks have been targeting.